Our freshwater native fish like to keep their cool. They’re used to shaded waterways lined with dense vegetation because over 80% of New Zealand was once forested.
Stream work for fish is important for restoring their populations. Riparian planting of streams has multiple positive outcomes for fish. Well planted stream edges help to:
- restore water quality by reducing sediment and nutrient run-off into the water
- strengthen stream banks – many native fish use bank overhangs and edges for shelter and laying eggs
- provide shelter from the Sun and heat
- encourage biodiversity and healthy insect populations that native fish rely on for food
- provide a moist, safe place for fish eggs to mature.
When planning to plant out stream edges, liaison with local organisations is very important to understand the particular stream and the species present and their needs. More information can be found in the resource Planning for change.
This resource outlines three steps for riparian planting planning. We suggest that this is used in conjunction with the teacher resource Planning for change, which includes links to important resources produced by NIWA.
Good site preparation will improve the success of your planting. Preparation should commence over summer, in readiness for planting over autumn and winter.
Some sites can be full of exotic weeds and pest plants, particularly near urban areas. Many weeds will overgrow native plants if they are left unchecked. Make sure you do a thorough job of removing weeds before planting out any natives. For very weedy sites, stage weed control and planting over several years. This allows you to tackle a small area at a time and also improves the transition between a weed-dominated system to a native one.
If your site is in rank grass, you can mow, lightly graze or spot spray with the appropriate herbicide or plant straight into it depending on the species. Be conscious that any sprays you use are not toxic to fish or likely to leach into the water. Sites with short grass can usually be planted directly into, but take care if there is kikuyu or pasture weeds that could overgrow your plants.
Remember that, in the absence of native trees and shrubs, birds, lizards and fish may be utilising the exotic weeds as habitat.
Autumn is the optimum time to plant. This allows plants time to establish over the colder, wetter months in readiness for the summer. For areas that suffer from heavy frosts, it can be best to wait until later in the season so that the young plants are not killed. Very wet sites are best planted in spring to early summer, once water levels have receded. This ensures that plants do not become waterlogged or washed away during the winter rains.
Which plants should I use?
The best way is to find a natural stream or wetland near your site. Observe what is growing naturally and try to recreate this pattern. Often, it is best to start with a few hardy species and allow others to colonise the site naturally over time. Alternatively, ‘diversity’ species can be added at a later date once the original hardy ‘pioneer plants’ are established.
The best species to plant depends on your location, so always source local information. Eco-sourcing plants is also a good way to assure the plants you select are acclimatised for local conditions. You can get advice on what and when to plant from your regional or district council or the Department of Conservation. These organisations and local nurseries can also offer advice on planting methods. For example, as a general rule, plant sedges 1 m apart, shrubs 1.5 m apart and trees 2–5 m apart. Where weeds are a problem, plants should be closer together to help shade them out.
Also keep in mind the issues of your particular stream when selecting plants. For example, if the stream has no shelter, you might want to look at putting in some fast-growing trees and shrubs such as mānuka, kānuka, karamū and cabbage trees. If your stream is in need of bank stabilisation, sedges, cabbage trees, lowland ribbonwood, karamū, tutu (poisonous to stock and humans), lemonwood and kōhūhū would be good choices.
Carex sedges, giant umbrella sedges and native toetoe near the stream edge provide homes for native fish, and if your stream restoration work is also looking to conserve native birds or encourage them back to your stream, consider kōwhai, karamū and harakeke.
Read about eco-sourcing and a citizen science initiative in Community conservation and a community nursery.
Maintenance is the key to successful planting. Many planted areas have inadequate weed control, causing high losses as weeds overgrow and kill native plants. Committing to regular maintenance will ensure that the efforts of preparing and planting the site have not been wasted.
New riparian plantings will need regular weed control for 3–4 years or until they are tall enough and dense enough to out compete weeds. New plantings should be checked once per month during spring and summer. Hand weeding around the base of each plant is all that is required. You will need to be particularly vigilant on sites that had lots of weeds originally or where there are weeds nearby that will colonise the site. You will need to replace any plantings that die, as leaving gaps may mean weeds move in.
A helpful tip when planting out is to make sure to place a stake next to each plant. This will help you find them when you are weeding and is a useful way to tell if any plants have died and need replacing. It is amazing how difficult it can be to relocate plants once the surrounding weeds have started to grow in spring and summer!
Keep pests away!
Remember pest control – rabbits, hares and possums like to nibble new plantings. Pest control can be conducted using traps or baits, with detailed information available from your regional council.
Urban solutions for water quality has additional information about this topic, including an example of successful community action.
The NZ Landcare Trust has a number of resources and a printable 70-page Community Urban Restoration & Education Guide aimed at people and organisations who are interested in getting involved in urban restoration work.
Check out the Weedbusters website for advice on dealing with problem weeds, or contact your local council for more information.